This invention relates to an x-ray mirror and material such as a total reflection mirror and a multilayer mirror reflective in the x-ray wavelength region.
In a catoptric system wherein the wavelength of the x-ray region, 0.1 .ANG. to 200 .ANG., is employed, a total reflecting mirror, a multilayer mirror, and so on are used depending on the use and the wavelength. If radiation is incident at a small oblique angle, the mirror of the catoptric system has an increased area and on the other hand the mirror of an optical system for a focusing and an imaging mirror has a reduced aperture and thereby an increased aberration. Therefore, it is preferable that the critical angle of x-ray radiation to the mirror surface in total reflection be large.
As regards reflecting material, high density substances such as Au and Pt are used because the critical angle of total reflection is in proportion to the density of the reflecting material. Au and Pt are chemically quite stable, and are thereby utilized for the reflecting surface because of the excellence of their reflecting property. In these reflecting mirrors, materials such as Au and Pt are deposited on a surface of a support substrate made of a material such as quartz glass, monocrystalline silicon, and SiC which can be polished to a very level form, by physical or chemical vapor deposition such as vacuum deposition and sputtering, or plating.
X-rays have a short wavelength, which is about 1/10-1/1000 of that of visible light. So, in order to obtain highly efficient reflectance in this wavelength region, the roughness of the reflecting surface and of the interface with the reflecting material support substrate must be reduced to about 1/10-1/1000 of that for visible light. Also in a substrate, such as one made of quartz glass, polished to have a level surface, the roughness of the film surface could be increased during deposition. Particularly, substances such as Pt and Au are low in Debye temperature and thereby the mobility of atoms at room temperature is large. As a result, crystal grains grows during vacuum deposition and sputtering, which will cause the roughness of the surface to increase. Further, a film 100-1000 .ANG. thick is deposited to form a total reflecting mirror. The film thickness of one layer of a multilayer mirror is between 10 .ANG. and 100 .ANG.. If the film is formed by the above-mentioned method, the density of the film tends to be reduced by about 5-30% as compared to that of a bulk material with the above film thickness. Therefore, x-ray reflecting performance can not be sufficiently obtained.